Early nutrition can have far-reaching effects on behavior: emerging research has revealed the existence of sensitive periods during postnatal development in which the developing brain has heightened sensitivity to environmental influences, including flavors of foods. While children's innate taste likes and dislikes create obstacles to healthy eating, research in humans and other animals has revealed that early experience can affect these likes and dislikes. The challenge is to determine whether there are optimum times when experience promotes greater liking of the flavors of healthy foods. Our previous experiments have shown that, as with other mammals, what a nursing mother eats during the first months of lactation can influence her child's food preferences. We propose to conduct a detailed randomized within- and between-subject study of women and their infants during a 16-month window, varying the timing and duration of exposure to three vegetable flavors (carrot, beet, and cabbage) to determine effects on the acceptance of these flavors by children, their mothers' own liking of these foods, and the likelihood that mothers will feed these foods to their children after weaning. Based on solid, previous research in humans and other animals, the over-arching goals of the proposed research are to specify the timing (Specific Aim 1) and consequences (Specific Aim 2) of the sensitive period for flavor learning in infants via flavor variety in mother's milk, and to determine the effects of reproductive state (Specific Aim 3) and genetic variation (Specific Aim 4) on vegetable liking in newly parturient mothers and their children. The hypotheses behind this research, examining highly pervasive and under-investigated behavioral phenomena surrounding how to introduce vegetables to children's diets, focus on early life, unlike many other studies that attempt to modify food habits in older children, and focus on the maternal-infant dyad because mothers' food consumption and feeding choices during the sensitive period may have far-reaching consequences for children's food exposures and choices later in life. Knowledge regarding the most efficacious time mothers should eat foods to develop preferences can lead to intervention strategies for both infants and their mothers, and consequently their families. Furthermore, knowledge about the timing of a sensitive period for learning about flavors in breast milk will shed light on long-term effects of not being exposed to these flavors early in life. The knowledge gleaned from this basic behavioral work could be translated to effective behavioral interventions to promote vegetable acceptance that are effective and implemented widely.